[LUM#5] Exploring the Universe
December 2013: The Sun gains a new satellite. The newest addition is named Gaia. Its mission: to explore a galaxy that is as close to us as it is little known—our own. And to help us better understand the universe…
50 billion data points: that’s what the European Gaia satellite—an explorer of the far reaches of our galaxy—sends us every day. It took no less than three years to begin deciphering this enormous amount of data, thanks to complex software, some of which was developed by the Montpellier Laboratory of the Universe and Particles (LUPM). Your computer, on the other hand, would have taken hundreds of years to do this work…
Mapping the galaxy
Comfortably positioned aroundthe “Lagrange point”1.5 million kilometers away—the precise location in the Sun-Earth system where the gravitational forces of the two bodies balance each other out—Gaia observes, catalogs, and calculates. And it’s helping us make giant leaps forward in our understanding of the Milky Way. For most of the objects observed by the satellite were previously poorly understood:“Gaia has collected data on 1.15 billion stars. That’s enormous! Until now, we only knew the distances to about 100,000 stars,” enthuses Gérard Jasniewicz, an astronomer at LUPM.
The primary objective of the Gaia mission is to measure the positions, distances, and movements of celestial objects within the galaxy. The stakes are high:“The goal is to create the most accurate three-dimensional map ever produced—and thereby to understand the very structure of our galaxy,” explains Fabrice Martins, also an astronomer at LUPM.
A galaxy that remains largely unknown. Why? First of all, because it is enormous. Want an idea of its size? If we could travel at the speed of light, it would take us about 100,000 years to cross it from one end to the other…“With Gaia, we’ll be able to accurately map all the bright stars in our galaxy located within 30,000 light-years,”explains Gérard Jasniewicz.
Time machine
One reason we know so little about the Milky Way is that we are part of it.“It’s paradoxical: in some respects, we know less about the Milky Way than we do about certain other galaxies,” Fabrice Martins continues. “We lack the necessary perspective to form a comprehensive picture of it. Many stars are hidden from us by clouds of gas and dust that form a curtain impenetrable to telescopes.”
The brightness, position, and velocity of stars: based on these fundamental data, the European satellite and its various instruments (see box) have much to teach us. In this vast undertaking, the task assigned to LUPM is crucial: to study the “radial velocities” of stars—their speed of approach or retreat.“Gaia will also reveal the intrinsic brightness of stars, and thus their mass: these are key data for characterizing them,” continues Fabrice Martins.
A way to better understand these brilliant populations—blue, white, yellow, orange, and red stars, as well as dwarfs, giants, and supergiants—that populate our galaxy. Many researchers at LUPM, who are working on star classification, are eagerly awaiting these results, which will allow them to test hypotheses, models, and theories. They are not alone. Gaia has captured the imagination of the global scientific community, which will have free access to all the project’s data. And which hopes to soon see new horizons open up across many disciplines…
New Horizons
As an explorer and cartographer of our galaxy, Gaia is also its archaeologist. The speeds, movements, but also the ages of stars and their chemical compositions: all these elements provide valuable insights into the galaxy’s past and how it formed.“A telescope is a time machine!” sums up Gérard Jasniewicz.
By the end of its mission—which is scheduled to last until 2020 but may well be extended—the Gaia satellite will have advanced our knowledge across the board, shedding light on a wide range of topics: quasars, exoplanets, asteroids, other galaxies… This galactic encyclopedia will even make it possible to verify the effects of universal gravity on a very large scale. And thus to test even the fundamental laws of physics. An encyclopedia so vast that scientists are already looking forward to the wealth of research topics it offers… and that will simply remain to be explored.
“Revolutionary”
“The Gaia project means‘more objects mapped, with greater precision, and over a wider range,’ as the scientists put it. A ‘revolutionary’ satellite that observes 50 million stars every day.”
Equipped with two telescopes, this technological marvel also features 106 sensors—the equivalent of a camera with a resolution of one billion pixels. 450 scientists from 25 European countries are working on this project led bythe European Space Agency (ESA ).
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